The invention is directed to a coupling arrangement for optically coupling a fiber to a planar optical waveguide integrated on a substrate whereby a fiber having an end face is secured in a groove having a V-shaped profile, the groove is fashioned in the substrate, the fiber end face facing at an end face of the planar waveguide.
A coupling arrangement of the said species is disclosed by European Patent Application 89 116 456.8, corresponding U.S. application Ser. No. 406,599, U.S. Pat. No. 4,973,133. In this coupling arrangement, the end face of the planar waveguide is arranged in an end face of the groove having a V-shaped profile. This groove is produced such that two slot-shaped channels are etched into the substrate proceeding obliquely toward one another into the depth from the surface until they meet or cross and, as a result thereof, a bridge or tongue separated from the substrate by the channels arises, this being cleaved off, for example in an ultrasound bath.
Channels having a V-shaped profile can also be manufactured by anisotropic etching in suitable materials, for example in a silicon crystal having the orientation 100. Since, however, the end faces of such grooves due to the anisotropic etching are not vertical but are oblique relative to the longitudinal axis of the groove, a fiber introduced into such a groove can have its end face brought toward the end face of the planar waveguide arranged in or at the oblique end face of the groove, but a relatively large spacing results between the end face of the fiber and the end face of the planar waveguide, causes high coupling losses between these end faces of the fiber and of the planar waveguide.